import { isES6Map, isObservableArray, isObservableMap } from "../internal"

declare var Symbol
const toString = Object.prototype.toString

export function deepEqual(a: any, b: any): boolean {
    return eq(a, b)
}

// Copied from https://github.com/jashkenas/underscore/blob/5c237a7c682fb68fd5378203f0bf22dce1624854/underscore.js#L1186-L1289
// Internal recursive comparison function for `isEqual`.
function eq(a: any, b: any, aStack?: any[], bStack?: any[]) {
    // Identical objects are equal. `0 === -0`, but they aren't identical.
    // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
    if (a === b) return a !== 0 || 1 / a === 1 / b
    // `null` or `undefined` only equal to itself (strict comparison).
    if (a == null || b == null) return false
    // `NaN`s are equivalent, but non-reflexive.
    if (a !== a) return b !== b
    // Exhaust primitive checks
    var type = typeof a
    if (type !== "function" && type !== "object" && typeof b != "object") return false
    return deepEq(a, b, aStack, bStack)
}

// Internal recursive comparison function for `isEqual`.
function deepEq(a: any, b: any, aStack?: any[], bStack?: any[]) {
    // Unwrap any wrapped objects.
    a = unwrap(a)
    b = unwrap(b)
    // Compare `[[Class]]` names.
    var className = toString.call(a)
    if (className !== toString.call(b)) return false
    switch (className) {
        // Strings, numbers, regular expressions, dates, and booleans are compared by value.
        case "[object RegExp]":
        // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
        case "[object String]":
            // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
            // equivalent to `new String("5")`.
            return "" + a === "" + b
        case "[object Number]":
            // `NaN`s are equivalent, but non-reflexive.
            // Object(NaN) is equivalent to NaN.
            if (+a !== +a) return +b !== +b
            // An `egal` comparison is performed for other numeric values.
            return +a === 0 ? 1 / +a === 1 / b : +a === +b
        case "[object Date]":
        case "[object Boolean]":
            // Coerce dates and booleans to numeric primitive values. Dates are compared by their
            // millisecond representations. Note that invalid dates with millisecond representations
            // of `NaN` are not equivalent.
            return +a === +b
        case "[object Symbol]":
            return (
                typeof Symbol !== "undefined" && Symbol.valueOf.call(a) === Symbol.valueOf.call(b)
            )
    }

    var areArrays = className === "[object Array]"
    if (!areArrays) {
        if (typeof a != "object" || typeof b != "object") return false

        // Objects with different constructors are not equivalent, but `Object`s or `Array`s
        // from different frames are.
        var aCtor = a.constructor,
            bCtor = b.constructor
        if (
            aCtor !== bCtor &&
            !(
                typeof aCtor === "function" &&
                aCtor instanceof aCtor &&
                typeof bCtor === "function" &&
                bCtor instanceof bCtor
            ) &&
            ("constructor" in a && "constructor" in b)
        ) {
            return false
        }
    }
    // Assume equality for cyclic structures. The algorithm for detecting cyclic
    // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.

    // Initializing stack of traversed objects.
    // It's done here since we only need them for objects and arrays comparison.
    aStack = aStack || []
    bStack = bStack || []
    var length = aStack.length
    while (length--) {
        // Linear search. Performance is inversely proportional to the number of
        // unique nested structures.
        if (aStack[length] === a) return bStack[length] === b
    }

    // Add the first object to the stack of traversed objects.
    aStack.push(a)
    bStack.push(b)

    // Recursively compare objects and arrays.
    if (areArrays) {
        // Compare array lengths to determine if a deep comparison is necessary.
        length = a.length
        if (length !== b.length) return false
        // Deep compare the contents, ignoring non-numeric properties.
        while (length--) {
            if (!eq(a[length], b[length], aStack, bStack)) return false
        }
    } else {
        // Deep compare objects.
        var keys = Object.keys(a),
            key
        length = keys.length
        // Ensure that both objects contain the same number of properties before comparing deep equality.
        if (Object.keys(b).length !== length) return false
        while (length--) {
            // Deep compare each member
            key = keys[length]
            if (!(has(b, key) && eq(a[key], b[key], aStack, bStack))) return false
        }
    }
    // Remove the first object from the stack of traversed objects.
    aStack.pop()
    bStack.pop()
    return true
}

function unwrap(a: any) {
    if (isObservableArray(a)) return a.slice()
    if (isES6Map(a) || isObservableMap(a)) return Array.from(a.entries())
    return a
}

function has(a: any, key: string) {
    return Object.prototype.hasOwnProperty.call(a, key)
}
